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Author Topic:   How big is our Galaxy.
jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 1 of 147 (278638)
01-13-2006 10:20 AM


One step in determining some minimum age for our universe would be to find out how big our local neighborhood is.
Our solar system, the backyard, is only one yard in the neighborhood of our galaxy, so how big is the galaxy?
Once we know the size of the neighborhood, the next question is "Where are we in relation to the center of the neighborhood?"
Suggested for Bible A&I

Replies to this message:
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 Message 5 by Wounded King, posted 01-13-2006 11:05 AM jar has not replied
 Message 7 by Clark, posted 01-13-2006 12:18 PM jar has replied
 Message 30 by MangyTiger, posted 01-13-2006 7:37 PM jar has not replied

  
AdminWounded
Inactive Member


Message 2 of 147 (278645)
01-13-2006 10:45 AM
Reply to: Message 1 by jar
01-13-2006 10:20 AM


As it stands this seems to be a perfect candidate for the Big bang and Cosmology forum to me. If you feel this is particularly relevant to the Accuracy and inerrancy forum could you try and frame your OP with that in mind?
TTFN,
AW

This message is a reply to:
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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 3 of 147 (278647)
01-13-2006 10:54 AM
Reply to: Message 2 by AdminWounded
01-13-2006 10:45 AM


Nah,I can accept that.

Aslan is not a Tame Lion

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AdminWounded
Inactive Member


Message 4 of 147 (278651)
01-13-2006 11:01 AM


Thread moved here from the Proposed New Topics forum.

  
Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 5 of 147 (278652)
01-13-2006 11:05 AM
Reply to: Message 1 by jar
01-13-2006 10:20 AM


All praise Monty Python
I know a song about this
Our galaxy itself contains 100 billion stars
It's 100,000 light years side to side,
It bulges in the middle, 16,000 light years thick
But out by us it's just 3,000 light years wide
Admittedly I'm not sure of the accuracy or derivation of these figures.
*ABE* Here is a page addressing the accuracy of the 'Galaxy song'.
TTFN,
WK
This message has been edited by Wounded King, 13-Jan-2006 05:17 PM

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Son Goku
Inactive Member


Message 6 of 147 (278654)
01-13-2006 11:14 AM


The Galaxy and the Local group are absolutely gigantic, is the easiest way of putting it.
For an analogy the distance between the Sun and pluto is about 3.6 billion miles.
If we then say that this distance is equivalent to the width of a blood cell, the galaxy is the size of a 10 meter diameter disk and the local group a sphere of 1 kilometer in diameter.
We are moderatly displaced to the bottom right of the local group if you were looking at the centre head on.

  
Clark
Inactive Member


Message 7 of 147 (278661)
01-13-2006 12:18 PM
Reply to: Message 1 by jar
01-13-2006 10:20 AM


Where are we in relation to the center of the neighborhood?
26,000 light years away from the center of the galaxy.
From today's Astronomy Picture of the Day: APOD: 2006 January 13 - Stars of the Galactic Center

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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 8 of 147 (278662)
01-13-2006 12:20 PM
Reply to: Message 7 by Clark
01-13-2006 12:18 PM


And this is an image we can actually see?

Aslan is not a Tame Lion

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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 9 of 147 (278663)
01-13-2006 12:21 PM
Reply to: Message 8 by jar
01-13-2006 12:20 PM


Only if you can see in infrared.
TTFN,
WK

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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 10 of 147 (278667)
01-13-2006 12:27 PM
Reply to: Message 9 by Wounded King
01-13-2006 12:21 PM


Well, while we cannot see in infrared, we can detect in infrared.
How do we determine that the galactic center is 26,000 light years away?

Aslan is not a Tame Lion

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Clark
Inactive Member


Message 11 of 147 (278669)
01-13-2006 12:35 PM
Reply to: Message 10 by jar
01-13-2006 12:27 PM


How do we determine that the galactic center is 26,000 light years away?
I don't know. Geometry?
This message has been edited by Clark, 01-13-2006 12:36 PM

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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 12 of 147 (278672)
01-13-2006 12:37 PM
Reply to: Message 10 by jar
01-13-2006 12:27 PM


I assume it is some sort of triangulation based upon our own relative motion compared to some reference objects and the galactic center.
Apparently som eearly estimates were base upon observing the motions of stars and using these observations to try and calculate their center of rotation.
Here we go, apparently efforts are in place to use 'Trigonometric Parallax' to measure the distance.
TTFN,
WK

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Matt P
Member (Idle past 4775 days)
Posts: 106
From: Tampa FL
Joined: 03-18-2005


Message 13 of 147 (278680)
01-13-2006 1:23 PM
Reply to: Message 10 by jar
01-13-2006 12:27 PM


Geometry in part, but also Cepheid variables
In the 1780s William Herschel observed all of the stars around our solar system and determined their distances. From this, he determined that we were at the center of the galaxy, as stellar density seemed to be homogeneous throughout the sky. Unfortunately, Herschel didn't realize that there was a large cloud of dark dust blocking our view of the center of the galaxy. Once infrared and radio astronomy became available, scientists in the 1960s penetrated this cloud and saw a slew of stars at the galactic center.
The distance to the galactic center was determined mostly by use of Cepheid variable stars, through the work of R.J.Trumpler:
Cepheid variable - Wikipedia
which are a "standard candle" for astronomy. To summarize this article, cepheid variables have a specific periodicity to their variance in luminosity, and by determining the period of a Cepheid variable, astronomers determine its suspected luminosity. Since luminosity correlates with distance, one can determine the distance to a Cepheid variable through this method.
Trumpler used Cepheid variable stars to determine the distance to globular clusters surrounding the galaxy and saw that they weren't distributed in the pattern we would expect if we were at the center of the galaxy, but were consistent with being off the center.
Later work with other wavelengths of life confirmed this.

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jar
Member (Idle past 394 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 14 of 147 (278685)
01-13-2006 1:29 PM
Reply to: Message 13 by Matt P
01-13-2006 1:23 PM


Re: Geometry in part, but also Cepheid variables
Later work with other wavelengths of life confirmed this.
I assume you mean light not life.
So currently, how accurate would you say the 26,000 light year distance to the Galactic Center and 100,000 Light year diameter figure for the local Galaxy is?

Aslan is not a Tame Lion

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Son Goku
Inactive Member


Message 15 of 147 (278699)
01-13-2006 2:37 PM
Reply to: Message 14 by jar
01-13-2006 1:29 PM


Re: Geometry in part, but also Cepheid variables
Very accurate. Its consistent across the whole structure, even when a shift is made to different methods for measuring distance.

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